Catheter leads for the intrathecal space and method of use

ABSTRACT

Various stimulation catheters are disclosed to lie along and stimulate tissue in the intrathecal space. The electrodes on the leads are various sizes to conserve the battery as well as allowing a more defined area of stimulation. It may also include multiple channels or passages for delivery of drugs, thermal or photonic energy. The sheath includes a fixing element configured to fix the electrode in place along the tissue.

CROSS-REFERENCE

[0001] This application claims priority of Provisional Applicationserial No. 60/225,823 filed Aug. 17, 2000.

BACKGROUND AND SUMMARY OF THE INVENTION

[0002] The present invention relates to an implanted tissue stimulatorsystem and catheters and more specifically for use in the intrathecalspace.

[0003] The concept of using electronic stimulation systems for thepurpose of controlling nerves or muscles is well known. These systemstypically utilize an implantable or an external pulse generator. Theexternal systems consist of a transmitter and antenna which transmitsenergy and/or stimulation signals transcutaneously through a patient'sskin to an implanted receiver. The receiver provides signal processingof the received pulses and transmits the energy derived therefrom toactivate electrodes implanted adjacent to specific types of tissue to bestimulated. A system like the one described above has been disclosedpreviously in U.S. Pat. No. 3,727,616. It is also known in prior artwhere more than one pair of electrodes are activated such as U.S. Pat.No. 3,449,768.

[0004] Problems arise in these prior art systems where electrodeplacement fails to provide the desired physical response. It may alsooccur later if a change in patient condition or electrode positionoccurs. This failure may also be caused by improper polarity of thestimulated electrodes relative to one another. Furthermore, it is oftenrequired that the electrodes be implanted surgically adjacent to one ormore nerve fibers. This type of procedure involves inherent risks due tothe fact that it is often performed in close proximity to the brain orspinal cord or other sensitive nerves or tissues. It is thereforedesirable to perform the electrode implantation only once to minimizethe surgical risks to the patient as well as the financial burdens.Moreover, even when a plurality of electrodes have been utilized, suchthat repeated surgical procedures are not required, the prior artsystems did not provide for dynamic programming and reprogramming ofdifferent electrodes after surgery until U.S. Pat. No. 4,459,989 toBorkan.

[0005] The Borkan patent '989 disclosed an external stimulator systemwhich allowed noninvasive programming of the stimulated electrodes. Eachelectrode was capable of assuming a positive, negative or open circuitstatus with respect to the other electrodes. This effectively allowedthe electrodes to be “repositioned” non-invasively. That sameprogramming ability (plus/minus/off) was later applied to totallyimplantable systems as well. The system had mono/biphasic control also.Further improvements are described in U.S. Pat. No 4,612,934 also toBorkan.

[0006] The application of spinal cord stimulation has shown itself to beeffective in the treatment of pain and is under study for various othermedical conditions. Initially, the leads were implanted by laminectomyand applied to the dura in the epidural space. The next generation ofelectrodes were positioned by percutaneous implantation. These wereeither placed into the intrathecal space or the epidural space. Due tothe construction and nature of the electrodes used at that time(approximately 30 years ago), numerous complications occurred with theuse of intrathecal catheter electrodes. These included CSF leakage. Inaddition, intrathecal electrodes were prone to significant movement andmigration (as were the early epidural leads).

[0007] Therefore, development efforts were focused on percutaneousimplantations in the epidural space. An example of a multielectrodecatheter assembly for spinal cord stimulation is shown in U.S. Pat. No.4,379,462 to Borkan.

[0008] Advances in catheter technology have allowed the widespreadapplication of intrathecal catheters that deliver drugs for variousmedical applications. In addition, various fixation means for cathetershave been developed and successfully utilized to eliminate the problemof electrode movement and migration. Therefore, it is now possible todevelop a catheter electrode for placement into the intrathecal spacewithout the problems and complications experienced previously.

[0009] The recent use of totally implantable stimulator systems with animplanted power source have resulted in increased emphasis on the amountof power required to deliver an effective stimulation regimen. Inaddition, use of multielectrode systems has put an even greater strainon the limited resources of an implanted power cell.

[0010] The intrathecal space provides a more direct means of deliveringeither drugs or electrical stimulation to the spinal cord. Bydefinition, implantation of devices in the epidural space placestimulation or drugs outside the dura, significantly further away fromthe spinal cord. Intrathecal placement therefore allows significantlyreduced levels of stimulation and drugs to create the same effect as acatheter placed epidurally.

[0011] Various stimulation catheters are disclosed to lie along andstimulate tissue in the intrathecal space. The electrodes on the leadsare various sizes to conserve the battery as well as allowing a moredefined area of stimulation. It may also include multiple channels orpassages for delivery of drugs, thermal or photonic energy. The sheathincludes a fixing element configured to fix the electrode in place alongthe tissue.

[0012] One embodiment of the intrathecal stimulation lead includes asheath having at least one electrode along the exterior of a distal endof the sheath to lie in-line along the tissue. The fixing element mayinclude at least one of the following: inflatable balloons, nitinol,tines and the sheath shape.

[0013] The sheath also include a passage extending from an inlet at theproximal end of the sheath to one or more outlets at the distal end ofthe sheath. The outlets may be located at one or more locationsincluding, but not limited to, the area between the electrodes and onthe electrodes. This passage may be used for dispensing of drugs. It mayalso be an optical channel or for a stilet to be used during positioningof the lead. This may be used without fixing elements.

[0014] Alternatively, one or more optical channels can be providedextending from a port at the proximal end of the sheath to a port at thedistal end of the sheath. The port for the optical channel at the distalend may be located at one or more of the tip of the distal end, the areabetween the electrodes and on the electrodes. The optical channel canprovide photonic energy to the tissue as well as functioning as a lensfor a remote camera. The passage which extends from the inlet of theproximal end of the sheath to one or more outlets at the distal end ofthe sheath may be used with at least one electrode along the exterior ofthe sheath to lie along the tissue to be stimulated. The same passage(or another) may also allow the use of a stilet during positioning ofthe lead.

[0015] In one embodiment, the electrodes extend no greater than 270°about the exterior of the sheath. The leads can extend anywhere in therange of 30°-270°. This reduces the surface area of the electrodes andtherefore the power required by the battery. It also allows theelectrodes to have a more defined or localized stimulation. Wherein theelectrodes extend less than 360° about the exterior of the sheath, thelength of the each electrode along the sheath should be typically atleast three millimeters. If the electrodes extends 360° about thesheath, the length of the electrodes along the sheath typically would bethree millimeters or less. The currently preferred length is two to fourmillimeters.

[0016] In another embodiment, an additional electrode spaced along thelength of the sheath from at least three in-line electrodes at thedistal end of the sheath. By positioning the additional lead on thesheath it is closer to the distal electrodes and thereby reduces thecurrent path compared to using the stimulator casing as the additionallead in a monopolar mode. The additional electrode has a surface area onthe sheath greater than the surface area on the sheath of each the atleast three electrodes. The additional electrode is typically at leasttwice the surface of the at least three electrodes and may be spaced,for example, at least 10 millimeters from the other electrodes. Theincrease in surface area can be by varying the length along the sheathor diminishing the circumference around the sheath of the electrodes.The lead may be activated in either a bipolar mode using two of the atleast three electrodes and in a monopolar mode using the additionalelectrode as a common anode and at least one of the other electrodes asa cathode.

[0017] A method of neurostimulation according to the invention includesinserting a catheter electrode assembly into the intrathecal space andpositioning it adjacent to the spinal cord. The catheter electrodeincludes a sheath having a distal and proximal end and at least threein-line electrodes along the exterior as well as a fixing element to fixthe electrode in place along the spinal cord. The electrodes are fixedat a desired location along the spinal cord using the fixing element.The stimulation pulses are provided to one or more of the electrodes.Where the catheter includes a passage with one or more ports at thedistal end of the catheter, the method further includes administering adrug through the passage.

[0018] The invention also anticipates an embodiment wherein theelectrodes extend no greater than 60° about the exterior of the sheath,the electrodes are positioned along the nerve root where it enters thespinal cord (dorsal root entry zone). Alternatively, where theelectrodes extend no greater than 90° about the exterior of the sheath,the electrodes may be positioned along the midline of the spinal cord tostimulate only the longitudinal and not the bending nerve fibers.

[0019] The catheter of the present invention can also be used for a drugtreatment method. This method includes positioning a stimulationcatheter adjacent to the tissue to be treated by the drug andadministering a drug to the patient via the catheter. The tissue is thenstimulated using the catheter. The catheter may include one or morecontacts at the distal end if the catheter stimulation is by electricenergy. As an alternative or in combination, an optical channel with oneor more ports at the distal end of the catheter would providestimulation by photonic energy. Alternatively, drugs may be administeredsystematically or concurrently with intrathecally administered agents.

[0020] The drug administered may be selected to be responsive tostimulation. Wherein the drug is responsive to light energy with aspecific wavelength, the stimulation of the tissue is with the lightenergy of that specific wavelength using the catheter. Wherein the drugis responsive to heat or cold, the tissue is stimulated with heat orcold using the catheter. The heat may be produced by electrical energyor photonic energy. The cold may be produced by a Peltier effect deviceor other means for example gas or liquids. An additional optical channelwith a port at the distal end of the catheter may be provided and isused to position the optical channel.

[0021] Finally, intrathecal stimulation by light energy may beadministered via the catheter—with or without drugs or electricalstimulation—to activate certain tissues. These tissues may, in somecases, be treated in some manner to increase their sensitivity to thismethod of activation and maybe used in combination with electricalstimulation.

[0022] Other objects, advantages and novel features of the presentinvention will become apparent from the following detailed descriptionof the invention when considered in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a cross-sectional view of a backbone and spinal cord.

[0024]FIG. 2 is a perspective view of a catheter lead having 270°electrodes incorporating the principles of the present invention.

[0025]FIG. 3 is a perspective view of a catheter lead with 90°electrodes positioned on the spinal cord.

[0026]FIG. 3A is a perspective view of the 90° electrode.

[0027]FIG. 4 is a perspective view of a catheter lead with a 60°electrode positioned on the spinal cord.

[0028]FIG. 4A is a perspective view of the 60° electrode.

[0029]FIG. 5 is a perspective view of a catheter lead with an additionalcommon anode electrode according to the principles of the presentinvention.

[0030]FIG. 6 is a perspective view of another catheter lead with anadditional common anode electrode.

[0031]FIG. 7 is a perspective view of a catheter lead including apassage having an outlet at the tip of the electrode and a balloonfixation device. Provision for an optional stilet is also shown.

[0032]FIG. 8 is a perspective view of a catheter lead with an outletbetween the electrodes and a nitinol fixation device deployed accordingto the principles of the present invention.

[0033]FIG. 8A shows the nitinol fixation device in position prior todeployment.

[0034]FIG. 9 is a perspective view of a catheter lead with a passagehaving an outlet on the electrode and a tine fixation device accordingto the principles of the present invention.

[0035]FIG. 10 is a perspective view of a catheter lead wherein thepassage is external the sheath according to the principles of thepresent invention.

[0036]FIG. 11 is a perspective view of a catheter electrode with apassage as well as two optical channels according to the principles ofthe present invention.

[0037]FIG. 12 is a nerve cuff lead employing the common anode principlesof the present invention.

[0038]FIG. 13 is a cross-sectional view of another catheter electrodewith a 90° electrode of reduced area according to the principles of thepresent invention.

[0039]FIG. 14 is a perspective view of a catheter electrode having abent distal end according to the principles of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Electrodes used for spinal cord stimulation are typicallyimplanted in the epidural space 23 between the vertebra 24 and the dura22, shown in FIG. 1. This is done for various reasons, including reducedcomplexity of the surgery, reduced potential complications, an increasedstability of the implant. However, implantation in the epidural spacerequires a significant amount of additional stimulation power since thesignal must be transmitted through the dura 22 and epidural space 23 andcerebrospinal fluid in order to reach its desired neural targets in thespinal cord 20. Anterior roots 25 and posterior roots 26 of the spinalcord 20 and Rami Communicantes 27 are also shown.

[0041] There were early stimulator leads 28 which were utilized in theintrathecal space 21 between the spinal cord 20 and the dura 22 withoutsuccess. Typically, these leads resulted in inconsistent stimulation,overstimulation and, generally, ineffective therapy. However, theyutilized technology approximately thirty years old. Due to developmentand implementation of better epidural leads, as well as the lack of aconcern for energy requirements (since they were using an externalbattery pack), this methodology was quickly abandoned.

[0042] More recently, intrathecal catheters have been utilizedextensively for administration of drugs including morphine and baclofenvia implantable drug pumps. Catheter complications were so prevalentthirty years ago (CSF leakage, migration, etc.) are no longer asignificant problem. Of course, administration of a drug does notrequire a precise electrode placement.

[0043] This new intrathecal neurostimulation electrode would uses forexample four millimeter electrode contacts (more forgiving when it comesto precise electrode placement) and yet would require dramatically lesspower (less than 20% of the power required for current epiduralelectrodes) because the electrodes would be in direct contact with theCSF and much closer to the desired neural targets. The primaryinsulating factor resulting in higher power requirements for epiduralleads is the lack of conductivity of the dura 22. The shunting effect ofelectrical current within the CSF is a much less significant factor.Therefore, an electrode designed with a stabilization means or fixingelements for use in the intrathecal space 21 utilizing materialsgenerally accepted in the art for intrathecal drug administration wouldprovide a unique, novel and advantageous method of stimulation of thespinal cord.

[0044] Fixation methods could include one or more of the following:inflatable balloons, tines which are either retractable with a stilet orsimply pliable enough to fit through a specially designed introducer ora novel shape (D shape) or the use of nitinol. Any of these fixationmethods, singly or in combination, can be used to provide stableelectrode placement on a long term basis.

[0045] The advantages of an intrathecal electrode are dramaticallyreduced size and/or increased life of a neurostimulator implant. Inaddition, implantation in the intrathecal space allows the use of alarger diameter electrode catheter and, therefore, more electrodes canbe placed, providing a wider selection of stimulation sites andstimulation paradigms. These stimulation paradigms could includesophisticated programs that switch stimulation between a number ofelectrodes slowly (over seconds or minutes, hours or days) to avoidaccommodation of the stimulation or could be fast (approximately thesame speed of the electrical activity of neurons in the spinal cord)artificially generating neural signals along the spinal cord 20 whichcould be perceived as any other sensory function with signals thattravel through the spinal cord. For instance, a signal could begenerated that would correspond to heat being applied to a patient's bigtoe, or pressure being applied to a patient's foot, or the sensation ofa limb in a different orientation than it actually is.

[0046] Theoretically, tastes, smells, sights or even thoughts could becreated in this manner allowing various artificial prosthesis (visual,auditory, etc.) to interface with the human body.

[0047] A first embodiment is illustrated in FIG. 2. A catheter lead 30includes a sheath 32 having a plurality of electrodes 34 at a distal end36 of the catheter 30. A proximal end 38 of the catheter 30 havecontacts 39 to be connected to a stimulator, not shown. There is onecontact 39 for each electrode 34. The length of the electrodes L₁ aregenerally two to four millimeters. The distance D₁ between theelectrodes is typically six millimeters, for example. The electrodes areshown to extend 270 degrees about the circumference of the catheter.

[0048] In order to achieve further increases in battery life, thesurface area of the active electrode contact can be reduced. Anelectrode with a specific orientation adjacent to the spinal cord wouldallow a 30°-270° electrode as opposed to the 360° electrodes used in allcurrent catheter electrodes. This would also enable the electrodes toremain at the preferred three or four millimeters in length making iteasier for physicians to hit the desired target and requiring fewerelectrode contacts in the lead (also allowing a smaller lead). Differentmeans could be used to stabilize the electrode in place, including (1)inflatable balloons, (2) nitinol, (3) novel shape electrodes, (4)mechanical system whereby tines are deployed upon removal of the stilet,(5) mechanical system of flexible tines.

[0049] A 270° electrode is illustrated in FIG. 2, a 90° electrode isillustrated in FIG. 3A and a 60° electrode is illustrated in FIG. 4A.

[0050] The small radius electrode, for example, 90° or less, allows afocused electrical stimulation field along the physiological midlinePM_(L) of the spinal cord 20 and reduces the effective stimulation fieldin the area of the bending fibers. As illustrated in FIG. 3, theelectrode 34 may also be placed at the nerve root midline NRM_(L) It iswell known that bending fibers are preferentially stimulated whencompared to longitudinal fibers. Thus, by positioning the lead adjacentto the desired longitudinal fibers, a focused stimulation of thelongitudinal fibers will take place.

[0051] The small electrodes in the range of 30°-60° also allowsselective activation of the fibers. This is particularly useful wherethe nerve enters the cord. Such placement is illustrated in FIG. 4,where the 60° electrode 34 is adjacent to the nerve roots 25,26.

[0052] For any of the above lead designs, an additional method ofdecreasing power requirements is to use monopolar stimulation. A largesurface area common anode electrode is used in conjunction with a singleelectrode in the desired stimulation area on the electrode contactarray. Monopolar stimulation is not new, but does provide theopportunity to decrease the power requirements for effectivestimulation.

[0053] The incorporation of a large surface area anode electrode somedistance away from the other active electrodes on the same catheter oralong the length of an intrathecal catheter has never been performed orattempted. In the prior systems, the casing of the stimulator acted asthe anode in a monopolar mode. Its distance from the distal electrodescreated a long current path. This new and novel approach reduces thecurrent path, creates a different field and also allows a unitaryelectrode system so that the stimulator device itself does not have tobe made in two different configurations (one with an active case anodeand one without). Therefore, a choice between bipolar and monopolarstimulation can be made after implantation using a stimulator (pulsegenerator) which could normally only provide bipolar stimulation.

[0054] As illustrated in FIG. 5, an additional electrode 35 is providedat the distal end 36 displaced from the other electrodes 34. Theelectrodes 34 are shown as 360° electrodes. As illustrated in FIG. 6,catheter electrode 40 includes a sheath 42 with having a plurality ofinline electrodes 44 and an additional electrode 45 on the wire orsheath extension 47 extending from the distal end or paddle 46. Theproximal end 48 has contacts 49 connected to each electrode and to astimulator.

[0055] The electrodes 34,44 all have a length L1 and the additionalelectrode 35,45 has a length L2. Length L2 is greater than L1, at leasttwice its length. Thus, for example, if length L1 is two millimeters,the length L2 is four millimeters. The length L2 may be anywhere between2-4 times that of the length L1. Also, it should be noted that theadditional electrode 35,45 is spaced by a distance D2 from the nearestelectrode 34,44. Where D1 is approximately six millimeters, the distanceD2 is at least 10 millimeters and can be as much as 20 millimeters. Withthis distance, the electrode acts as a point source when used inconjunction with a second electrode. The electrodes 34,44 act as a pointsource when used in conjunction with the additional electrode 35,45 ofthe increased area.

[0056] Alternatively, a common anode or additional electrode 35 may bethe same length as the other electrodes 34, but have a greatercircumferential dimension than that of the electrode 34. This wouldincrease the surface area of the additional electrode 35 relative to theother electrodes 34. Therefore, the electrodes 34 may be in the 30° to270° configuration previously described. The separation differencebetween the electrodes 34 and that of 35 will allow operation asdescribed with respect to FIGS. 5 and 6. Such an electrode isillustrated in FIG. 12 to be discussed below.

[0057] A catheter lead capable of stimulation electrically as well asdispensing drugs is illustrated in FIGS. 7-11. The catheter lead 50 hasa sheath 52 with inline electrodes 54 spaced along the distal end 56. Atthe proximal end 58, terminal contacts 59 are connected internally toeach of the electrodes shown. A passage 60 is provided in the sheath 50.In FIG. 7, an outlet 62 is provided in the tip of the distal end 56 anda balloon fixation device 63 is shown. Provision is also made for anoptional stilet which is removable and may be used to assist inplacement of the catheter. Various stilets 61 of different shapes andcharacteristics may be used with these leads.

[0058] In FIG. 8, the outlet 64 is shown in the space between theelectrodes 54 and a nitinol fixation device 65 is shown in the deployedcondition. In FIG. 8A, nitinol fixation device 65 is shown prior to thedeployment through opening 53 in sheath 52. In FIG. 9, the outlet 64 isshown in or on the electrode 54 and a tine fixation device 67 is shown.

[0059] Although one fixation is illustrated on a specific Figure, anyfixation device may be used with any of the catheters. Fixation methodsmay also include devices that are actively deployed and/or retracted(for instance by a stilet) in addition to the methods shown herein.Also, the fixation device may be located at any or more than onelocation or position along the catheter. A fixation device should beused where the catheter electrode is installed in the intrathecal space.

[0060] While FIGS. 7-9 show the passage 60 internal to the sheath 52, anexternal delivery 68 may be used as shown in FIG. 10.

[0061] The electrode catheter 50 may also include a single or pair ofoptical channels 70 and 72 having outlets or ports in the distal end.The fiberoptic channels and light energy delivered through a cleartranslucent area in the catheter is illustrated in FIG. 11. One of thechannels can provide a source of light to be used as a further source ofstimulation. The other channel will form a lens for a camera or othermonitoring devices. The camera can be used in positioning the electrodeor distal end. Channel 60 with outlet 64 is also shown for a drugdelivery.

[0062] It should be noted that only a single optical path can be used toprovide a source of light for a photon stimulation without the passage60 or the outlet 64. It should also be noted that the passage 60 orexternal passage 68 for drug delivery may be used in combination withthe light channel 70 without the electrodes 54. Although two channels70, 72 are shown, any number of channels could be used and could includea combination of different types of channels—working channels forinstruments, optical channels for light or camera, stilets etc.

[0063] The catheter of FIGS. 7-11 may be used in a percutaneous drugtreatment method. The drug is administered to the patient and thestimulation cathode is positioned adjacent the tissue to be treated bythe drug. The tissue is then stimulated using the catheter. This allowsselective and localized drug treatment. Certain compounds changechemically when stimulated. Compounds can also be delivered viaelectropheretic means.

[0064] The intrathecal location of this catheter places it past theblood/brain barrier and therefore offers numerous unique opportunitiesfor combination stimulation/drug treatment regimes. In addition,application of various forms of energy (heat, cold, etc.) independentlyor with stimulation allow indirect alteration of brain chemistry. Alsothe production of heat in a tissue may make the tissue more susceptibleto absorption of a drug. The drug may be administered through thepassage 60 or 68. The source of stimulation and/or the drugs may beexternal to the body or totally implantable. The implantable systemcould include a microprocessor, pump, port and an external port forrefilling the pump or selection of a different drug or fluid.

[0065] The drug may be stimulated by electrical energy using theelectrodes 54 or by photonic energy using the optic channel 70. Heat maybe produced by either the electrodes 54 or the optical channel 70. Coldmay be produced by a Peltier effect chip or other means, for example gasor liquids. If the drug is responsive to light energy of a specificwavelength, the stimulation uses light energy of that specificwavelength.

[0066] Finally, intrathecal stimulation by light energy may beadministered via the catheter—with or without drugs or electricalstimulation—to activate certain tissues. These tissues may, in somecases, be treated in some manner to increase their sensitivity to thismethod of activation and maybe used in combination with electricalstimulation.

[0067] The lead 50 as illustrated in FIG. 12 is curved at its distal end56 which includes the electrodes 54. Sheath 52 includes a wire extension57 which includes the additional anode electrode 55 and the electricalcontact 59. The curved distal end 56 wraps around the spinal cord or thenerves. This is another form of a fixing device. The stilet 61 can beinserted through passage 60 to maintain the distal end 56 linear untilit is adjacent to the nerve or the spinal cord. The passage 60 may thenbe used for fluid delivery.

[0068] Different shape stilets may be used (bent tips for example) toimprove steerability during positioning of the catheter, as illustratedin FIG. 14.

[0069] Additional electrode 55 has the same length L1 along the sheath52 or wire 57 as does the electrodes 54. The difference is thatelectrodes 54 are illustrated as 270° electrodes, whereas additionalelectrode 55 is a 180° electrode. This difference in circumferentialdimension provides the difference in surface area. This provides theminimum 2 to 1 surface area as previously discussed. obviously, thedistance D₁ between electrodes 54 is substantially less than thedistance D₂ between electrodes 54 and 55.

[0070] A modified 90° electrode is illustrated in cross-section in FIG.13. Electrode 54 has a smaller radius or diameter A than sheath's 52radius or diameter B. For example, the diameter A may be 0.0045 inchesand diameter B may be 0.065 inches. The shape of the sheath andelectrode allows introduction through a standard introducer needle. Itstill offers a reduced area electrode 54 and a stabilizing shape whichmay be used with or without tines or other fixation means.

[0071] Although the invention has been described for use with animplanted stimulator system (externally or internally powered), itshould be noted that the same type of regime can be delivered by anon-implantable device. Applications for such non-implantable systemscould include intra-operative testing of a stimulator system prior toimplantation. An external stimulator system is connected to animplantable electrode for a period of trial stimulation prior todetermining whether an implantation should be performed.

[0072] Although the present invention has been described and illustratedin detail, it is to be clearly understood that the same is by way ofillustration and example only, and is not to be taken by way oflimitation. The spirit and scope of the present invention are to belimited only by the terms of the appended claims.

What is claimed:
 1. A stimulation lead to lie along and stimulate tissuecomprising: a sheath to be placed in the intrathecal space having adistal and proximal end; at least one electrode along the exterior ofthe distal end of the sheath to lie along tissue; a fixing element onthe sheath configured to fix the electrodes in place along the tissue;and a passage extending from an inlet at the proximal end of the sheathto one or more outlets at the distal end of the sheath.
 2. A leadaccording to claim 1, wherein the fixing element includes at least oneof inflatable balloon, nitinol, tines, and sheath shape.
 3. A leadaccording to claim 1, wherein the outlets are at one or more of the tipof the distal end, the adjacent to the tip of the distal end and on theelectrode.
 4. A lead according to claim 1, including an optical fiber inthe passage.
 5. A lead according to claim 1, including one or moreoptical channels extending from a port on the proximal end of the sheathto a port at the distal end of the sheath.
 6. A lead according to claim5, wherein the port at the distal end is at one or more of the tip ofthe distal end, adjacent to the tip of the distal end and on one or moreof the electrode contacts.
 7. A lead according to claim 1, including anadditional electrode spaced from the at least three electrodes spacedalong the exterior of the sheath; and the additional electrode having asurface area length on the sheath greater than the surface area of eachof the at least three electrodes.
 8. A lead according to claim 7,wherein the additional electrode is at least twice the surface area ofthe at least three electrodes.
 9. A lead according to claim 7, whereinthe additional electrode is spaced from the at least three electrodes byat least ten millimeters.
 10. A lead according to claim 7, wherein thesheath includes a wire extension extending from its distal end to itsproximal end and the additional electrode is on the wire extension. 11.A lead according to claim 1, including at least three electrodes spacedalong the exterior of the sheath, and the electrodes each extend nogreater than 270 degrees about the exterior of the sheath.
 12. A leadaccording to claim 1, including at least three electrodes spaced alongthe exterior of the sheath, and the electrodes each extend no greaterthan 90 degrees about the exterior of the sheath.
 13. A lead accordingto claim 1, including at least three electrodes spaced along theexterior of the sheath, and the electrodes each extend no greater than60 degrees about the exterior of the sheath.
 14. A method ofneurostimulation using a catheter electrode assembly including a sheathhaving a distal and proximal end, at least three in-line electrodesspaced along the exterior of the distal end of the sheath to lie in-linealong the spinal cord, and a fixing element configured to fix theelectrodes in place along the spinal cord; the method comprising:inserting a catheter electrode assembly into the intrathecal space andpositioning adjacent a spinal cord; fixing the electrodes at a desiredlocation along the spinal cord using the fixing element; and providingstimulation pulses to a selected pair of electrodes.
 15. The methodaccording to claim 14, wherein the catheter includes a passage with oneor more ports at a distal end of the catheter and includingadministering a drug through the passage.
 16. The method according toclaim 14, wherein the electrodes each extend no greater than 60 degreesabout the exterior of the sheath and the electrodes are positioned alonga nerve root where it enters the spinal cord.
 17. The method accordingto claim 14, wherein the electrodes each extend no greater than 90degrees about the exterior of the sheath and the electrodes arepositioned along a midline of the spinal cord.
 18. The method accordingto claim 14, wherein the catheter includes an optical channel with oneor more ports at a distal end of the catheter and including providingstimulating pulse of photonic energy to the optical channel incombination with or in lieu of the pulses to the electrodes.
 19. Amethod of drug treatment comprising: positioning a stimulation catheterin the intrathecal space; administering drugs via the catheter; andstimulating the tissue using the catheter.
 20. The method according toclaim 19, wherein the catheter includes one or more electrodes at thedistal end and the stimulation is by electric energy.
 21. The methodaccording to claim 19, wherein the catheter includes an optical channelwith one or more ports at a distal end of the catheter and thestimulation is by photonic energy.
 22. The method according to claim 19,wherein the catheter includes a passage with one or more ports at adistal end of the catheter and the drug is administered through thepassage.
 23. The method according to claim 19, wherein the drugadministered is selected to be responsive to stimulation.
 24. The methodaccording to claim 23, wherein the drug administered is responsive tolight energy of a specific wave length and including stimulating thetissue with light energy of the specific wave length using the catheter.25. The method according to claim 23, wherein the drug administered isresponsive to heat and including stimulating the tissue with heat usingthe catheter.
 26. The method according to claim 23, wherein the drugadministered is responsive to cold and including stimulating the tissuewith cold using the catheter.
 27. The method according to claim 19,wherein the catheter includes an optical channel with a port at a distalend of the catheter and the catheter is positioned using the opticalchannel.
 28. A catheter to lie along and stimulate tissue comprising: asheath having a distal and proximal end; at least one electrode alongthe exterior of the distal end of the sheath to lie along tissue; and apassage extending from an inlet at the proximal end of the sheath to oneor more outlets at the distal end of the sheath.
 29. A lead according toclaim 28, wherein the outlets are at one or more of the tip of thedistal end, the adjacent to the tip of the distal end and on theelectrode.
 30. A lead according to claim 28, including an optical fiberin the passage.
 31. A lead according to claim 28, including one or moreoptical channels extending from a port at the proximal end of the sheathto a port at the distal end of the sheath.
 32. A lead according to claim31, wherein the port at the distal end is at one or more of the tip ofthe distal end, adjacent to the tip of the distal end and on one or moreof the electrode contacts.